1. Field of the Invention
This invention relates generally to an electronic image printing apparatus and, more particularly, to an electronic image printing apparatus in which the same scanning optics that laser address a liquid crystal light valve also subsequently project film exposing illumination through the addressed light valve.
2. Description of the Prior Art
Electronic image printing apparatus of the type using a laser addressed liquid crystal light valve addressed by a laser diode are known in the art. One such electronic image printing apparatus reported by Sony utilizes a laser addressed liquid crystal light valve doped with a squarylium IR absorbing dye in cyanononyl biphenyl in concentrations of up to 0.4 wt percent. Such laser addressed liquid crystal light valves have been matched with semi-conductor lasers using a 10 milliwatt Ga-Al-Ar laser of 780 nanometer lasing wavelength. The laser beam is deflected in the XY directions by galvanometer meters and thereafter focused onto the liquid crystal light valve by a suitable focusing lens. The galvanometers operate to scan the laser beam across the area of the liquid crystal light valve whereupon the laser energy is absorbed by the IR dye and transformed into heat to cause smectic A-nematic isotropic phase transition of the liquid crystal molecules. This isotropic state of the liquid crystal molecules possesses a randomly oriented order which operates to scatter light and thus show a dark image when the light valve is illuminated for projection onto a photosensitive surface. The liquid crystal light valve is ordinarily maintained at a constant temperature in a temperature chamber a few degrees below the smectic A-nematic phase transition temperature thus insuring that the liquid crystal molecules do not realign until deliberately erased upon the application of an AC bias across the liquid crystal.
The aforementioned electronic image printing apparatus disclosed by Sony operates to uniformly illuminate the liquid crystal light valve from the side opposite to which it is previously addressed by the laser beam resulting in the light valve reflecting the uniform illumination through an appropriate projection lens to expose a photosensitive material. Operating the liquid crystal light valve in this reflection mode, however, limits the contrast ratio which could otherwise be achieved were the liquid crystal light valve operated in a transmission mode. Projecting a beam of incoherent light to uniformly illuminate the liquid crystal light valve in the aforementioned transmission mode after it is laser addressed presents other difficulties resulting from the injection of a dichroic beam splitter in the light path between the galvanometer mirrors and the liquid crystal light valve. The dichroic beam splitter positioned in this manner inhibits the galvanometer mirrors from being used to line scan an existent photograph to derive electronic image data therefrom which may be subsequently utilized to provide an enhanced image reproduction thereof.
Therefore, it is a primary object of this invention to provide an electronic image printing apparatus having a single set of XY scanning galvanometer mirrors which may be utilized to line scan an original photograph to derive image data therefrom and thereafter utilized to addressably line scan a laser beam across the face of a liquid crystal light valve.
It is a further object of this invention to provide an electronic image printing apparatus in which a single pair of XY scanning galvanometer mirrors are utilized to addressably line scan a liquid crystal light valve and to reflect a beam of incoherent light from a projection lamp to the light valve.
It is an even further object of this invention to provide an electronic image printing apparatus having a single set of XY scanning galvanometer mirrors for scanning an original photograph in order to derive image data therefrom, for subsequently addressably line scanning a laser beam across the surface of a liquid crystal light valve, and for thereafter reflecting a beam of incoherent light from a projection lamp for transmission and modulation by the light valve to ultimately expose a photocopy of the original line scanned photograph.
Other objects of the invention will be in part obvious and will in part appear hereinafter. The invention accordingly comprises a mechanism and system possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.